Mechanical damage of metallic subterranean natural gas pipelines can be measured by a variety of methods, including impulse diffraction, ultrasonic and electromagnetic techniques. Because of the limited penetration depth, impulse diffraction is restricted to measurements of gross characteristics, generally in a limited environment. Ultrasonic techniques measure the velocity of ultrasonic waves in the metals themselves and relate those measurements to stress or breaks. There are however, difficulties in differentiating stress effects from the texture of the material and this becomes ineffective in non-metallic natural gas pipeline structures. With electromagnetic techniques, one or more of the magnetic properties (such as permeability, magnetostriction, hysteresis, coercive force, or magnetic domain wall motion during magnetization) of a ferromagnetic material are sensed and can be correlated to damage or stress yet again this is limited to the metallic characteristics of the natural gas pipeline.
The aforementioned techniques rely on detecting the change in magnetic properties of the material caused by stress which is known as the magnetoelastic effects. Many of these techniques are difficult to implement without a controlled samples available while the measurement is being done. In addition, these techniques are less sensitive to changes in the magnetic properties of ferromagnetic materials caused by stress other than nonlinear harmonics techniques. Methods such as pigging which, involves a device moving through the pipeline at a relatively high rate of speed, are also means of experimental testing within a pipeline however, are inappropriate for real-time damage detection and prediction.
Detection and characterization of the wireless communication signal conveyance caused by mechanical or dialectic change of or within the pipelines or the earthen duct defined by pipelines, particularly natural gas transmission pipelines, is important because of the danger to pipeline integrity posed by third party damage or tampering as well as the need to optimize the infrastucture operations.
Therefore, there exists a need for more efficient systems and methods of providing operational and/or integrity monitoring either on a continuous basis or on an as needed bases and can operate through metallic and/or non-metallic natural gas pipelines.